An arrangement for blocking the operation by an operator of machinery is disclosed in U.S. Pat. No. 4,613,845. The arrangement prevents a driver, who is intoxicated, from starting a motor vehicle. For this purpose, an alcohol sensor and a distance sensor are mounted on the steering wheel of the vehicle and are connected via an evaluating unit to on-board electronics of the motor vehicle. The distance sensor recognizes the operational readiness of the alcohol sensor and ensures that the alcohol sensor is not covered by a foil. Starting the vehicle is prevented if the alcohol sensor supplies a measured value which indicates a significant breath alcohol content.
Alcohol measuring devices are known which measure the alcohol content in a person through the skin and which permit a continuous wear thereof by means of a belt which is applied about the arm or the leg. In this way, measured values are available which continuously show the alcohol concentration. The measured data is transmitted to a central station by a data line. Such a measuring device is disclosed in international patent publication WO 94/07407 (PCT/US 92/08196).
U.S. Pat. No. 4,912,458 discloses a so-called sobriety interlock system wherein the driver must blow a breath sample into a measuring device before starting the vehicle which then evaluates the breath sample with respect to alcohol content and the manner in which the breath sample is supplied. It is disadvantageous in such an arrangement that another person can observe that the driver has outputted a breath alcohol sample for starting the vehicle.